The present invention relates to a management device and a management method, and is suitably applicable to, for instance, a storage system.
Conventionally, a user of a storage system calculates a fixed logical capacity of a volume to be used by the user, and creates and utilizes a volume to which is allocated a storage area equivalent to the logical capacity. This requires a user to prepare in advance a storage corresponding to a logical capacity in anticipation of future changes in business operations, despite the fact that the logical capacity will not be initially used. In the following description, such a volume to which a fixed storage area is allocated in advance shall be referred to as a normal volume.
On the other hand, a virtualized volume function has been proposed in recent years as a function of storage devices. The virtualized volume function is a function that presents a virtualized volume (hereinafter referred to as a virtual volume) to a host device as a volume to be used by a user to read and write data, and which dynamically allocates on the virtual volume a storage area for storing data according to the use status of the virtual volume. According to such a virtualized volume function, since it will suffice to sequentially purchase additional storages corresponding to required logic capacities, effective use of the storage resources in the storage device may be achieved.
However, since a user consciously uses the respective volumes separately from each other, normal volumes and virtual volumes will coexist in a storage system that includes a storage device having a virtual volume function.
Cases where a user selects a virtual volume may include a case where the user would like to configure in advance a volume with a large capacity because the user does not wish to reallocate a volume by sudden writing even though the logical capacity required by business operations is not known in advance.
Meanwhile, cases where a user selects a normal volume may include a case where an essential logical capacity for business operations is known in advance or a case of preventing the occurrence of a state where a necessary capacity cannot be allocated due to a depletion of free space of an aggregate (hereinafter referred to as a virtual pool) of an original volume that allocates storage area to a virtual volume.
In addition, since a virtual volume requires mapping management between a logic volume and a physical volume, its performance is inferior to that of a normal volume. Therefore, a normal volume is also selected for cases where high efficiency of data input and output is required. Furthermore, with the virtualized volume function, a plurality of virtual volumes shares a virtual pool and physical volumes. As a result, there is a disadvantage in that a failure of a physical volume may affect a plurality of virtual volumes. Thus, there are cases where a normal volume is selected from the perspective of maintainability.
As seen, a user uses both normal volumes and virtual volumes based on applications, characteristics and the like, and a change in application may result in data migration performed from a normal volume to a virtual volume or vice versa. Various techniques regarding migration of data stored in volumes have been proposed by the present inventors (Japanese Patent Laid-Open No. 2006-099748, Japanese Patent Laid-Open No. 2006-302077).